A known valve structure, which is applicable to an air pump as an example, includes a first fluid chamber 100, a second fluid chamber 200/300, a partition wall 210 for partitioning the first and second fluid chambers 100 and 200/300, a communicating hole, which is provided at the partition wall to establish a fluid communication between the first and second fluid chambers 100 and 200, and a valve body 230/240, which is also provided at the partition wall, for example, as illustrated in FIG. 7. The valve body 230/240 includes a flexible valve portion 230a/240a formed in an umbrella shape for occluding the communicating hole. The valve portion 230a of the valve body 230 is provided at the partition wall 210 at a first fluid chamber side, for example. In such a structure, when a fluid pressure generated in the second fluid chamber 200 is lower than a fluid pressure generated in the first fluid chamber 100, the valve portion 230a is flexibly deformed towards the partition wall 210 (i.e., in a direction where an end portion of the valve portion 230a approaches the partition wall 210), thereby occluding the communicating hole. On the other hand, when the fluid pressure of the second fluid chamber 200 is higher than the first fluid chamber 100, the valve portion 230a of the valve body 230 is flexibly deformed in a direction to be away from the partition wall 210, thereby opening the communicating hole. Thus, the valve body 230 structures a check valve (non-return valve) for allowing a fluid communication from the second fluid chamber 200 to the first fluid chamber 100.
According to such valve structure, the valve body 230 is simply provided at the partition wall 210. Such valve structure is disclosed in JP2006-266414A as an example.
According to the known valve structure, when high fluid pressure is generated in the first and second fluid chambers 100 and 200, the fluid inside the second fluid chamber 200 spouts out from the communicating hole provided at the partition wall 210 in response to the difference between the fluid pressure generated in the first fluid chamber 100 and the fluid pressure generated in the second fluid chamber 200. The spouting fluid makes contact with the umbrella shaped valve portion 230a, and the valve portion 230 is accordingly deformed in the direction to be away from the partition wall 210. At this time, when a large pressure difference is generated between the first and second fluid chambers 100 and 200 and the fluid accordingly spouts from the communicating hole at high pressure, the umbrella shaped valve portion 230a is deformed to be approximately inside out, i.e., the umbrella shaped valve portion 230a is deformed in a direction opposite to a base portion 230c of the valve body 230, as illustrated in FIG. 7. When the valve portion 230a is deformed in such manner, a large strain is generated at a connecting portion between the valve portion 230a and the base portion 230c. Furthermore, in a condition where the valve portion 230a is frequently and repetitively deformed in such manner, the connecting portion between the valve portion 230a and the base portion 230c is fatigued, and a crack may be generated thereat. In the same manner, in a structure where the valve portion 240a of the valve body 240 is provided at the partition wall 210 at a second fluid chamber side and the valve portion 240a is deformed for allowing and interrupting a fluid communication from the first fluid chamber 100 to the second fluid chamber 200, the umbrella shaped valve portion 240a is deformed in a direction opposite to a base portion 240c of the valve body 240, and a connecting portion between the valve portion 240a and the base portion 240c is fatigued to generate a crack thereat.
A need thus exists for a valve structure, which is not susceptible to the drawback mentioned above.